Chem.Ber. 1939, 72, 675-677, J. Chem. Soc., 1956, 4280-4283 and J. Chem. Soc.(C), 1971, 1805 describe the synthesis of 6-phenylphenanthridines. The International Applications WO 97/28131, WO 97/35854, WO 99/05111 and WO 99/05113 describe 6-phenyl- and 6-pyridylphenanthridines as PDE4 inhibitors.